Wheel Speed Sensor

Fig. 7 Wheel sensor:

Four electronic variable reluctance wheel sensor assemblies, are used in the Anti-Lock brake system. Each sensor is connected to the electronic controller by electrical wiring and has an adjustable air gap between the sensor head and tooth surface.
The rear sensors are mounted on brackets bolted to the rear disc brake axle adapters. The toothed rear sensor rings are pressed on the axle shafts, inboard of the axle shaft flange.
The front sensors are mounted on brackets bolted to the front spindles. The front toothed sensor rings are pressed onto the inside of the front rotors.
The front sensor air gap is 1.3mm (0.051-in), the rear sensor air gap is 1.1mm (0.043-in).